An organic light emitting diode so-called bottom emission type structure is configured of a lamination of transparent electrodes (anodes), a hole injection layer, a hole transport layer, light emitting layers, an electron transport layer, an electron injection layer, metal electrodes (cathodes) and so on. In addition, in a top emission type one, reflective electrodes (anodes), a hole injection layer, a hole transport layer, light emitting layers, an electron transport layer, an electron injection layer, metal electrodes (cathodes) of semitransparent extremely thin and so on are laminated on a substrate made of a glass plate, a polyimide film of brownish-red or the like, which are not necessarily transparent. An apparatus of manufacturing a bottom emission type organic light emitting diode, which is general for industrially manufacturing the organic light emitting diode by vapor deposition, comprises a substrate holder for holding a transparent substrate, on which transparent electrodes are formed on a vapor deposition target surface, so that the vapor deposition target surface faces downward, a driving mechanism for rotating or translating the substrate holder or vapor deposition sources at a constant speed in a predetermined direction, and a plurality of point-like or linear vapor deposition sources provided so as to face the vapor deposition target surface of the transparent substrate held on the substrate holder in a bottom portion in a vacuum chamber. In each of a plurality of the vapor deposition sources, a deposition material for forming the hole injection layer, the hole transport layer, the light emitting layers, the electron transport layer, the electron injection layer, the metal electrodes, and so on is contained.
Vapor deposition masks corresponding to patterns of respective layers are prepared in the inside of the vacuum chamber used to deposit the materials of the above mentioned respective layers. For forming each layer, it is exchanged to a vapor deposition mask corresponding to the layer to be formed. In case of a full color organic light emitting diode without using a color filter, in order to deposit light emitting layers corresponding to colors of R (red), G (green) and B (blue), vapor deposition masks having openings corresponding to the patterns of respective colors are provided. When a light emitting layer of each color is formed, it is exchanged to a vapor deposition mask corresponding to the color. The vapor deposition mask needs to be closely attached to the vapor deposition target surface of the transparent substrate held on the substrate holder. The most common conventional vapor deposition mask is a metal mask having openings of a predetermined pattern formed thereon, and the substrate is closely attracted to and held on the vapor deposition target surface of the transparent substrate by a magnetic force of a magnet provided in the back side of the holder, that is, in the side opposite to the transparent substrate held on the substrate holder.
In order to make the openings much fine while maintaining the strength of the vapor deposition mask, as shown in FIG. 6, a conventional vapor deposition mask 110 described in Patent Literature 1 comprises a mask body portion 111 having a plurality of through openings 113, and a peripheral portion 112 having a thickness greater than a thickness of the mask body portion and having bottomed openings 114 larger than the through openings 113. The vapor deposition mask 110 is manufactured by the processes of forming a first resist pattern on a metal plate which has of the same sizes and arrangement pattern as those of a plurality of the through openings 113, forming a plurality of the through openings 113 on the metal plate by performing etching process via the through openings of the first resist pattern, removing the first resist pattern, forming a second resist pattern having a plurality of second through openings on the metal plate for exposing the metal edges of a predetermined width around a plurality of the through openings 113 respectively, and forming the bottomed openings 114 around a plurality of the though openings 113 by performing etching process via the second through openings of the second resist pattern. However, in the vapor deposition mask 110 manufactured by performing etching processes on such a metal plate, it is substantially impossible to form the through openings 113 uniformly on the entire surface of the vapor deposition mask 110 due to the occurrence of etching unevenness, for example, so that it was difficult to manufacture the vapor deposition mask corresponding to a high-definition thin film pattern more than 300 ppi, for example. In addition, since the vapor deposition materials are radially scattered from the vapor deposition sources, the inner shadows 115, that is, shadow portions where no vapor deposition material adheres, are formed due to the edge portions of the through openings 113 and the bottomed openings 114. Although, it is possible to deposit the deposition materials also on the initially shaded portions where no deposition material was adhered by rotating or translating the substrate holder, the thickness of the deposition materials adhering on the vapor deposition target surface become uneven.
On the other hand, in order to solve the problem of the vapor deposition mask manufactured by etching processes, as shown in FIG. 7, a conventional composite-type vapor deposition mask 120 described in Patent Literature 2 is manufactured by laminating a resin film layer 121 where a plurality of through openings 123 is formed and a holding member 122 made of a metal thin plate and holding the resin film layer 121 where a plurality of through openings 124 is formed. In the vapor deposition mask 120, a plurality of the through openings 124 which is larger in size than the thin film pattern to be formed on a transparent substrate is formed by performing etching process or the like to a magnetic metal plate previously, then, the resin film layer 12 is adhered on a surface of the holding member 122, and the through openings 123 corresponding to the thin film pattern are formed by irradiating laser beams on the resin film layer 121 via the through openings 124. In the vapor deposition mask 120, since the through openings 123 are formed by irradiating the laser beams on the resin film layer 121, it is possible to form a high-definition thin film pattern in comparison with the vapor deposition mask 110 formed by etching the metal plate. However, when it is attempted to form a much higher-definition thin film pattern, positional accuracy of the through openings 124 to be formed in the holding member 122 is required, and due to the positional deviation from the through openings 123 to be formed in the resin film layer 121, the inner shadows may be expanded, or the shapes of the inner shadows may become uneven.
Furthermore, in this conventional composite-type vapor deposition mask 120, subsequent to forming the resin film layer 121 by spreading a thermosetting resin on a surface of a glass substrate or the like and baking the same, the resin film layer 121 is temporarily removed and adhered on a surface of the holding member 122. Then, in order to form the through opening 123 by the laser beams, alcohol such as ethanol is spread on the surface of the glass plate, and the resin film layer 121 on the vapor deposition mask 120 is closely to the surface of the glass substrate by the surface tension of the alcohol again, so that it is difficult to attach the resin film layer 121 to the surface of the glass substrate without generating air bubbles. Here, in case of sublimating the resin material in the depth direction by irradiating the laser beams on the resin film layer 121, distribution also occurs in a speed for penetrated through the resin film layer 121 is depending on the in-plane distribution of energy. In consideration of forming one through opening, there are edges that can be quickly and slowly cut out among the edges of the four sides. At that time, when a bubble is interposed between the glass substrate and the resin film layer 121, a small piece, which invades into a gap formed by the bubble with the slowly cut side as the base point, occurs. The small piece is called burr. Therefore, there is a possibility that burrs are generated in the surroundings of the through openings 123 formed by irradiating the laser beams in the conventional vapor deposition mask 120. Generally, when the burr faces the opening, the burr serves as a barrier and causes the inner shadow, and when it does not face the opening, it causes a gap created between the deposition target substrate and the vapor deposition mask, and it causes the outer shadow which is adhesion of deposition materials adhere to places where the deposition material should not be adhered, essentially. In the following description, both of the inner shadow and the outer shadow are collectively referred as “vapor deposition shadow”.
Alternatively, in order to prevent the vapor deposition shadows from enlarging due to the edge portions of the openings formed on the holding member, in a vapor deposition mask 130 described in Patent Literature 3, as shown in FIG. 8, a plurality of through openings 134 are formed by irradiating laser beams on a resin film formed of a lamination of a base layer 131 not containing a magnetic material, a magnetic layer 132 containing a magnetic material powder, and a protective layer 133. Since this vapor deposition mask 130 has no holding member, it is thinner than the vapor deposition mask 110 or 120 described in Patent Literature 1 or Patent Literature 2, so that the vapor deposition shadows can be made smaller, and, a much higher-definition thin film pattern can be formed. However, since the thickness of the magnetic layer 132 is thin, in a state where the transparent substrate held by the substrate holder is interposed, attraction force by a magnetic force of a magnet provided in the substrate holder is weak and the vapor deposition mask 130 may not be closely attracted to and held on the surface of the transparent substrate.